Question

Excited about being ready to do my first git push ever, I created an alias for PuTTY in my cygwin environment:

alias ssh="/cygdrive/c/PROGRA~2/putty/PUTTY.EXE"

Then invoked (inside my working directory, of course), just as explained in page 47 in the git community book:

git push ssh://mylinuxserver/~winwin/gitrepo master:master

My excitement didn’t last very long, as it immediately failed with a fatal error:

error: cannot run ssh: No such file or directory
fatal: unable to fork

Considering that I am able to run successfully, from the same exact command line and shell instance, ssh winwin@mylinuxserver I am very surprised to receive this error message.

Any idea why this is happening and how to fix this?

UPDATE I: Thanks to this guide, I discovered that PUTTY.EXE is not the correct exe to use in git. Instead, one should be using PLINK.EXE.

That guide also hints that an environment variable, named GIT_SSH, should be used to let git know how to do the magic. So, I:

~/sb/ws> export GIT_SSH=/cygdrive/c/PROGRA~2/putty/PLINK.EXE
~/sb/ws> git push ssh://mylinuxserver/~winwin/gitrepo master:master

And now I am receiving a different error:

fatal: The remote end hung up unexpectedly

I consider this progress in the right direction but I still don’t know how to solve the problem. Any idea would be very appreciated.

UPDATE II: Still trying to troubleshoot this mystery. This time I suspected that since git push doesn’t prompt for username+password anywhere, authentication must lie within the keys… So, I double-checked sshd configuration per this howto. The only thing I found as needing change was uncommenting the line HostKey /etc/ssh/ssh_host_dsa_key in /etc/ssh/sshd_config and restarting the service service sshd restart. The first time after that, $GIT_SSH did prompt for confirming the server’s dss key fingerprint and I confirmed storing the key in cache, but… The problem still persists:

fatal: The remote end hung up unexpectedly

Additional ideas?

(PuTTY’s registry now contain two keys for the same server: rsa2@22:mylinuxserver and dss@22:mylinuxserver. Hmmm… I am not sure what this means)

More diagnostic info: Typing $GIT_SSH -v yields:

~/sb/ws> $GIT_SSH -v
Looking up host "mylinuxserver"
Connecting to 192.168.1.2 port 22
Server version: SSH-2.0-OpenSSH_4.2
We claim version: SSH-2.0-PuTTY_Release_0.60
Using SSH protocol version 2
Doing Diffie-Hellman group exchange
Doing Diffie-Hellman key exchange with hash SHA-1
Host key fingerprint is:
ssh-dss 1024 c8:77:42:4f:76:29:56:4c:ea:b0:11:6a:a6:3c:6a:f7
Initialised AES-256 SDCTR client->server encryption
Initialised HMAC-SHA1 client->server MAC algorithm
Initialised AES-256 SDCTR server->client encryption
Initialised HMAC-SHA1 server->client MAC algorithm
login as: winwin
winwin@mylinuxserver's password:
Sent password
Access granted
Opened channel for session
Allocated pty (ospeed 38400bps, ispeed 38400bps)
Started a shell/command
Last login: Wed Jul 13 21:41:12 2011 from winmachine

Can you spot anything suspicious?

Getting there: By far the best guide for my situation: Git, SSH, PuTTY.

Insights:

1. $GIT_SSH -agent must be run once
2. PAGEANT.EXE must be running in the background (and private key added to it via its systray icon!)
3. PUTTYGEN.EXE must be used to generate a public/private keys pair
4. dss not mandatory, rsa is good enough.
5. More? (unless $GIT_SSH -2 -C -i C:\\Users\\winwin\\SSH\\private.ppk succeeds without password prompt, there is no point to even try git push…)

After copying & pasting the public key from PuTTY Key Generator to /home/winwin/.ssh/authorized_keys in mylinuxserver a new message showed up in response to the command in insight #5 above:

Server refused our key

This is a good sign… 🙂 I think I am on my way to solving the mystery.

UPDATE III: After changing StrictModes to no in /etc/ssh/sshd_config on the sshd server, I managed to succeed with $GIT_SSH -2 -C -i C:\\Users\\winwin\\SSH\\private.ppk. It still prompts for the username, though (but doesn’t prompt for password).

git push ssh://mylinuxserver/~winwin/gitrepo master:master continues to fail however — with the same error message:

fatal: The remote end hung up unexpectedly

This is insane.

UPDATE IV: The -l username parameter to PLINK is key. I managed to make git push login successfully, by creating a 1-line shell script /cygdrive/c/PROGRA~2/putty/PLINK.EXE -l winwin $* and exporting the the entire script’s path to $GIT_SSH, but “the remote end still hangs up unexpectedly”.

This is what I am getting on the client (Windows/PuTTY) side:

~/sb/ws> git push ssh://mylinuxserver/~winwin/gitrepo master:master
Environment:
  USER=winwin
  LOGNAME=winwin
  HOME=/home/winwin
  PATH=/usr/local/bin:/bin:/usr/bin
  MAIL=/var/mail/winwin
  SHELL=/bin/bash
  SSH_CLIENT=192.168.1.8 50951 22
  SSH_CONNECTION=192.168.1.8 50951 192.168.14.2 22
bash: mylinuxserver: command not found
fatal: The remote end hung up unexpectedly

And This is what I am getting on the server side (Linux/sshd) side:

debug1: sshd version OpenSSH_4.2p1
debug1: read PEM private key done: type RSA
debug1: private host key: #0 type 1 RSA
debug1: read PEM private key done: type DSA
debug1: private host key: #1 type 2 DSA
debug1: rexec_argv[0]='/usr/sbin/sshd'
debug1: rexec_argv[1]='-d'
debug1: Bind to port 22 on ::.
Server listening on :: port 22.
debug1: Bind to port 22 on 0.0.0.0.
Bind to port 22 on 0.0.0.0 failed: Address already in use.
debug1: Server will not fork when running in debugging mode.
debug1: rexec start in 4 out 4 newsock 4 pipe -1 sock 7
debug1: inetd sockets after dupping: 3, 3
Connection from 192.168.1.8 port 50951
debug1: Client protocol version 2.0; client software version PuTTY_Release_0.60
debug1: no match: PuTTY_Release_0.60
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_4.2
debug1: permanently_set_uid: 74/74
debug1: list_hostkey_types: ssh-rsa,ssh-dss
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: client->server aes256-ctr hmac-sha1 none
debug1: kex: server->client aes256-ctr hmac-sha1 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received
debug1: SSH2_MSG_KEX_DH_GEX_GROUP sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_INIT
debug1: SSH2_MSG_KEX_DH_GEX_REPLY sent
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: KEX done

debug1: userauth-request for user winwin service ssh-connection method none
debug1: attempt 0 failures 0
debug1: PAM: initializing for "winwin"
debug1: PAM: setting PAM_RHOST to "win7client"
debug1: PAM: setting PAM_TTY to "ssh"
Failed none for winwin from 192.168.1.8 port 50951 ssh2
debug1: userauth-request for user winwin service ssh-connection method publickey
debug1: attempt 1 failures 1
debug1: test whether pkalg/pkblob are acceptable
debug1: temporarily_use_uid: 513/513 (e=0/0)
debug1: trying public key file /home/winwin/.ssh/authorized_keys
debug1: matching key found: file /home/winwin/.ssh/authorized_keys, line 1
Found matching RSA key: bd:a6:4a:6a:04:43:8d:60:d9:bf:66:de:51:13:83:66
debug1: restore_uid: 0/0
Postponed publickey for winwin from 192.168.1.8 port 50951 ssh2
debug1: userauth-request for user winwin service ssh-connection method publickey
debug1: attempt 2 failures 1
debug1: temporarily_use_uid: 513/513 (e=0/0)
debug1: trying public key file /home/winwin/.ssh/authorized_keys
debug1: matching key found: file /home/winwin/.ssh/authorized_keys, line 1
Found matching RSA key: bd:a6:4a:6a:04:43:8d:60:d9:bf:66:de:51:13:83:66
debug1: restore_uid: 0/0
debug1: ssh_rsa_verify: signature correct
debug1: do_pam_account: called
Accepted publickey for winwin from 192.168.1.8 port 50951 ssh2
debug1: monitor_child_preauth: winwin has been authenticated by privileged process
Accepted publickey for winwin from 192.168.1.8 port 50951 ssh2
debug1: PAM: reinitializing credentials
debug1: permanently_set_uid: 513/513
debug1: Entering interactive session for SSH2.
debug1: server_init_dispatch_20
debug1: server_input_channel_open: ctype session rchan 256 win 16384 max 16384
debug1: input_session_request
debug1: channel 0: new [server-session]
debug1: session_new: init
debug1: session_new: session 0
debug1: session_open: channel 0
debug1: session_open: session 0: link with channel 0
debug1: server_input_channel_open: confirm session
debug1: server_input_channel_req: channel 0 request exec reply 1
debug1: session_by_channel: session 0 channel 0
debug1: session_input_channel_req: session 0 req exec
debug1: Received SIGCHLD.
debug1: session_by_pid: pid 3441
debug1: session_exit_message: session 0 channel 0 pid 3441
debug1: session_exit_message: release channel 0
debug1: session_close: session 0 pid 3441
debug1: channel 0: free: server-session, nchannels 1

Connection closed by 192.168.1.8
debug1: do_cleanup
debug1: PAM: cleanup
Closing connection to 192.168.1.8
debug1: PAM: cleanup

Last clue needed…

1. What does bash: mylinuxserver: command not found mean?
2. What is git push trying to run?
3. Which command?
4. On the client or the SSH server?

Answer 1

I never succeeded making git work with PuTTY. Further time investment on my side didn’t seem to justify ROI, so I am giving up.